The bcl-2 Gene Product Prevents Programmed Cell Death of Ventricular Myocytes

BACKGROUND: To formally test whether the antiapoptotic protein bcl-2 would prevent programmed cell death in cardiac muscle cells provoked by p53, a known trigger of apoptosis in a variety of different cell types, we used replication defective adenovirus encoding either the bcl-2 and p53 genes to deliver bcl-2 and p53 to ventricular myocytes with high efficiency and uniformity. METHODS AND RESULTS: Vital staining of ventricular myocytes revealed a significant (7-fold, P<.05) increase in myocyte cell death in the presence of p53 in contrast to uninfected cells or those infected with a control virus. In addition, in the presence of p53, nucleosomal DNA fragmentation observed by Hoescht 33258 staining and terminal transferase deoxynucleotide end labeling indicated a significant increase in apoptotic cardiac nuclei compared with control cells, confirming the hypothesis that p53 alone is sufficient to trigger apoptosis of ventricular myocytes. Moreover, a significant increase in transcription of the bax promoter was seen in the presence but not in the absence of p53 compared with control cells. Expression of the antiapoptotic gene bcl-2 in ventricular myocytes was sufficient to prevent ventricular myocyte death and apoptosis provoked by p53. Importantly, the antiapoptotic effects of bcl-2 were independent of altered p53 expression or localization of p53 to cardiac nuclei. However, p53 dependent transcription of bax was repressed 4-fold (P<.05) by bcl-2, suggesting a tentative link between p53-mediated apoptosis and the protective properties conferred by bcl-2 in ventricular myocytes. CONCLUSIONS: To our knowledge, the data provide the first indication for the operation of bcl-2 in ventricular myocytes as an antiapoptotic factor.